U.S. Coast Guard officials have collected samples of an unidentified sheen discovered near the site of the Deepwater Horizon Platform wreckage off the Louisiana coast, officials said.

The substance was found by remote-operated vehicles (ROV) in the area of the drilling rig that exploded in the Gulf of Mexico in April 2010, killing 11 offshore workers and injuring at least 16 others. The Coast Guard's ROV operations ended Saturday, said Ensign Glenn Sanchez of the Coast Guard's New Orleans command center.

The unidentified substance was seen emitting from several areas of the rig wreckage, and samples were collected for further lab analysis. The site is about 40 miles southeast of the Louisiana coast.

"The monitors of the ROV inspections at the scene reported that it (sheen) was inconsistent with oil," Sanchez said. "We don't know what it is. Samples were taken, and we're trying to identify that."

No apparent source of the surface sheen has been determined, Capt. Duke Walker, federal on-scene coordinator for Deepwater Horizon, stated in a press release.

Officials will continue to monitor the sheen via satellite "while future steps are being considered," the release states.